"I ran to school."
Translation:Jag sprang till skolan.
This is a case where English can use the indefinite without an article but we can't in Swedish. The opposite is more common – we have combinations like köpa bil which is literally 'buy car', but you can't say just buy car in English, you need an article. Those combinations work like a unit – 'go to school' is an action in itself, it doesn't matter if you're thinking of a specific school or not, and köpa bil denotes the action of buying a car, any car. I don't think there's any reason why one language chose to encode one action but not the other that way.